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Poster: Administrator, Curator, or Staffsimon c Date: Jul 18, 2004 4:46am
Forum: prelinger Subject: Re: Any chance of properly re-digitizing any of these films from the masters?

Sounds to me like some kind of script-based conversion to 352*480 would be our first port of call, but obviously, we don't want to ruin the aspect ratio - also, some say that 352*480 is somewhat non-standard as well?

[With the amount of new material we have to put online, I think we'd rather find a programmatic way to fix the existing movies than have to re-digitize from scratch, which is v.timeconsuming.]

Anyhow, feedback and suggestions are welcome. We're trying to make it much easier for people to burn DVDs of the material now that so many people are getting DVD burners.

Thanks,
Simon.
[Archive admin.]

This post was modified by simon c on 2004-07-18 11:46:04

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Poster: Steve Nordby Date: Jul 18, 2004 9:05am
Forum: prelinger Subject: Re: Any chance of properly re-digitizing any of these films from the masters?

DVD's are supposed to support previous VCD and SVCD resolutions 352x240, 352x480, and 480x480, as well as 704x480 (2xVCD) and 720x480. Converting other aspect ratios is slow and in my experience results in jerky motion of objects moving horizontally in the picture.

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Poster: WaverBoy Date: Jul 18, 2004 5:46am
Forum: prelinger Subject: 352x480?

I don't see why you'd want to convert them to 352x480; wouldn't the ratio would still be squeezed? 352 wide, 480 high. Why not just convert them to the DVD standard, or 720x480? By the way, a friend of mine more knowledgeable than I just informed me that, after converting to 720x480, the raw mpeg file will still play a bit vertically squished on the computer, but when authored to DVD and played on a DVD player, it will play normally.

For some reason, the person who encoded the files at 368x480 thought they would come out looking ok, according to the info at this site:

"The files were encoded at constant bitrates ranging from 2.75 Mbps to 3.5 Mbps. Most were encoded at 480 x 480 pixels (2/3 D1) or 368 x 480 (roughly 1/2 D1). The encoder drops horizontal pixels during the digitizing process, which during decoding are interpolated by the decoder to produce a 720 x 480 picture. (Rod Hewitt's site Coolstf shows examples of an image before and after this process.)"

I'm not sure which decoder is being talked about here, but these files are not remotely compatible with DVD.

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Poster: Administrator, Curator, or Staffsimon c Date: Jul 18, 2004 6:23am
Forum: prelinger Subject: Re: 352x480?

It's worth remembering that these files were being encoded in early 2001, when affordable DVD burners were but a theoretical idea. Nonetheless, I agree it's rather vexing.

I was suggesting conversion to 352x480 because it would mean a very similar filesize, and then, I hoped, would then play correctly in the DVD version - it sounds like movie players like Windows Media Player currently aren't getting the right stretching info, because of the non-standard width.

I _think_ that converting it to 352*480 and making sure that info was properly embedded in the MPEG would result in basically the correct aspect ratio. [I don't know if that's easy/possible.]

http://www.videohelp.com/forum/userguides/174200.php

..explains:

'Remember the WIDTH doesn't matter, since the width is 'hard coded' so to speak, when you encode the video. The width is always stretched to the full playback width according to the aspect ratio on the MPEG (MPEG Aspect Ratio (1.333*480 for svcd for example). Thats why a CVD (352x480) looks 'right', just like an SVCD (480x480) looks right. Both stretch back out to 640x480 with a 4:3 MPEG aspect ratio. View them with any software player that doesn't understand the 'Aspect Ratio Property', and you'll see very tall, very skinny people.'

So I suspect the current 368*480 MPEG 2s have busted aspect ratio info, at least in some players, hence the issue.

The only worry would be whether that 16 pixel loss would result in noticable squashing (it'd be horizontally squashed about 5 percent, right?)

See what I mean?
s!

PS - I am _not_ a coder or author of the derivers, just the forum admin trying to work out what's wrong.

This post was modified by simon c on 2004-07-18 13:23:32

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Poster: WaverBoy Date: Jul 18, 2004 9:18am
Forum: prelinger Subject: To clarify...

"It's worth remembering that these files were being encoded in early 2001, when affordable DVD burners were but a theoretical idea. Nonetheless, I agree it's rather vexing."

I understand; I'm just trying to figure out how to fix it now that the damage has been done. :)

"I was suggesting conversion to 352x480 because it would mean a very similar filesize, and then, I hoped, would then play correctly in the DVD version - it sounds like movie players like Windows Media Player currently aren't getting the right stretching info, because of the non-standard width.

I _think_ that converting it to 352*480 and making sure that info was properly embedded in the MPEG would result in basically the correct aspect ratio. [I don't know if that's easy/possible.]"

Again, why 352x480? Even if the ratio will be correct--if the trouble is going to be taken to convert in the first place, why not just do 720x480, the DVD standard? Unless you want to keep the smaller file size to conserve server space and speed up download times, in which case I would offer that, from what I've read, the emphasis here at the Archive seems to be on quality, and I would think that converting to the DVD standard would achieve the best results. Of course, I could be way off base here, and often am.

"http://www.videohelp.com/forum/userguides/174200.php

..explains:

'Remember the WIDTH doesn't matter, since the width is 'hard coded' so to speak, when you encode the video. The width is always stretched to the full playback width according to the aspect ratio on the MPEG (MPEG Aspect Ratio (1.333*480 for svcd for example). Thats why a CVD (352x480) looks 'right', just like an SVCD (480x480) looks right. Both stretch back out to 640x480 with a 4:3 MPEG aspect ratio. View them with any software player that doesn't understand the 'Aspect Ratio Property', and you'll see very tall, very skinny people.'"

Thanks for that info; understood.

"So I suspect the current 368*480 MPEG 2s have busted aspect ratio info, at least in some players, hence the issue."

The main issue with 368x480 is that it isn't compatible with DVD at >all<.

"The only worry would be whether that 16 pixel loss would result in noticable squashing (it'd be horizontally squashed about 5 percent, right?)

See what I mean?"

I see what you mean. I do know that, if encoded to the 720x480 DVD standard, although the raw mpeg file will be squished a bit during playback on Windows Media Player, DVD playback will be correct. I've now tested it. I can't vouch for 352x480. Anyone?

"PS - I am _not_ a coder or author of the derivers, just the forum admin trying to work out what's wrong."

Hey, I'm sure you know more about it than me! I assure you I meant no disrespect whatsoever; please let me know if I've stepped on any toes, and if I have, don't hesitate to rap my knuckles (or toes) a bit. :o I'm just trying to understand this craziness. Whoever decreed that there should be 12 zillion different video formats/resolutions/ratios/framerates should have their toenails removed with icepicks. :)

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Poster: Administrator, Curator, or Staffsimon c Date: Jul 18, 2004 10:02am
Forum: prelinger Subject: Re: To clarify...

Cool,

I think we're talking about the same thing, so I shall take this info back to our 'flotilla of technical experts' and see what we can do with it.

Thanks again,
s!

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Poster: WaverBoy Date: Jul 19, 2004 1:21pm
Forum: prelinger Subject: Re: To clarify...

Simon, just let me say a big hearty THANK YOU for getting back to my questions so promptly, and another equally hearty THANK YOU to all involved at the Archive in preserving and digitizing these films for present and future generations to enjoy and learn from. I may have come across as ungrateful in my first few posts, and I'd like to assert that I'm anything but.

Thanks again,

Jeff